Plant Community- definition, concept and structure

1. Community: Definition,
Concept and Structure
Dr. Emasushan Minj
Assistant Professor
Department of Botany

2. • Definition of Community:
“Community represents the population of all
species living and interacting in an area at a
particular time.”
• Population is defined as an adaptation to changes in
environmental conditions within limits.
• The key driving force of adaptation to environmental changes is
believed to be biological evolution, the change in a population’s
genetic makeup through successive generation.

3. Concept of Community:
• A group of organisms comprise population. Each population has
characteristics like natality, mortality, age structure, growth dynamics and
so on.
• Several populations share a common habitat and its resources; they
interact among themselves and develop into a biotic community.
• Microorganisms, plants and animals populations sharing a common
habitat and interacting among themselves develop into biotic
communities.
• The composition of a biotic community in any habitat is dependent upon
the occurrence of environmental conditions in that habitat and the
ecological amplitude of species populations.

4. • Thus the climate and other abiotic as well as biotic conditions of a
habitat determine the type of community which survives and develops.
• The organisms of a community usually exhibit trophic (feeding)
relationships among themselves.
• They also interact in sharing the space and there may be interactions at a
reproductive and behavioral level.
• Each biotic community exhibits a number of characteristics, such as
diversity, density, dominance, composition and stratification, within its
special limit.
• The transitional zone or junction between two or more diverse
communities is called “ecotone”.
• The ecotone is a community termed as ecotonal community with
organisms of overlapping communities and some of unique types.

5. Structure of Community:
• Communities may be small, consisting of few species populations in a
small space, or large, comprise several species populations in a large area.
• The community structures, composition and other characteristics can be
readily described by visual observation without actual measurement.
• This is a qualitative approach which is easier than the quantitative
population analysis where measurements are actually made.
• Communities usually categories by the ecologists in various ways
primarily based of habitat features like water availability, high exposure,
or other habitat features.
• For instance, depending on the amount of water availability, plant
communities may be hydrophytic (aquatic habitats), mesophytic
(moderately moist soil habitat) and xerophytic (dry or arid habitat).

6. • Similarly communities growing on conditions of abundant light are called
heliophytic and those growing in shade sciophytic.
• Identically communities growing on various habitats designated as desert
communities, mountain communities and estuarine communities and so
on.
• In general, a community is dynamic since it changes over time. This
dynamic nature is reflected in the succession of organisms in a habitat.
• A series of changes results in the development of a relatively stable
community, which maintains its structure and influences the climate of the
area.
• Such a stable and mature community is called a climax community, while
communities of successional stages are called seral communities.
• The plant community structures, composition and other characterize can be
described in both qualitative and quantitative means.

7. Community Dynamics:
• Communities are dynamic systems constantly interacting with another
system, the environment, which is equally dynamic.
• The community charges are gradual and imperceptible at any time but eas-
ily recognizable if observed at regular intervals over a long period of time.
• Seasonal changes in plant communities always occur at every place,
particularly in areas where temperature variation is significant.
• However, in course of very long period of time at many places the
communities have reached a peak stage and attained a dynamic balance
with the environmental changes.
• The process of change in communities and their environment at one place
in the course of time is called “ecological succession”.

8. Thank you